1. Field of the Invention
The present invention relates to a boat steering device and system.
2. Description of the Related Art
Outboard motors typically include an internal combustion engine that drives a propulsion propeller. Such motors are provided on the outside of a boat hull, and a steering motor usually is provided for horizontally rotating the outboard motor. For example, in Japanese Patent No. 2959044, a steering motor is provided to a connecting part between the hull and the outboard motor. A boat propulsion unit actuator connected by a signal cable to a steering wheel adjacent an operator's seat. A rotation angle sensor is provided on the steering wheel, and the steering motor operates according to the rotational direction and the rotation angle of the steering wheel as detected by the rotation angle sensor in order to steer the outboard motor.
A force necessary for steering an outboard motor varies continuously depending on certain conditions such as the speed of the boat, the rotation angle and the steering speed of the outboard motor, the relationship between the rotational direction of a propeller of the outboard motor and the steering direction of the outboard motor, and the boat weight. External forces such as waves and wind are also relevant. Therefore, the amount of torque necessary for the steering motor to steer the outboard motor varies continuously.
However, the device of Japanese Patent No. 2959044 does not contemplate adjusting the amount of torque generated by the steering motor. Also, the efficiency of a motor generally decreases depending on the increase of the amount of torque. Therefore, there is a problem that the efficiency of the steering motor decreases when the amount of torque increases.
Further, the amount of torque generation of the steering motor also varies according to changes in conditions of the motor itself such as the temperature of the motor. Consequently, there is a problem that the efficiency of the steering motor decreases with changing conditions.